Sprocket

ABSTRACT

A sprocket includes first teeth having a first maximum width, and second teeth having a second maximum width greater than the first maximum width alternately arranged with the first teeth. The second teeth have a leading surface relative to a drive direction of the sprocket, a lateral surface at the second maximum width, and a relief between the leading surface and the lateral surface, with a midline of the lateral surface being offset relative to a plane extended radially through a center of a respective tooth.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority under 35 U.S.C. §119(e) to U.S. Provisional Patent Application Ser. No. 61/937,738 filed on Feb. 10, 2014, and incorporated herein by reference.

This application is related to U.S. Non-Provisional patent application Ser. No. ______ (Attorney Docket No. W1420.101.102) filed on even date herewith, U.S. Non-Provisional patent application Ser. No. ______ (Attorney Docket No. W1420.102.102) filed on even date herewith, and U.S. Non-Provisional patent application Ser. No. ______ (Attorney Docket No. W1420.104.102) filed on even date herewith.

BACKGROUND

The present disclosure relates generally to sprockets and, more specifically, relates to a sprocket having alternating wide and narrow teeth for use as a chainring on a bicycle.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a left-front perspective view of one example of a sprocket in accordance with the present disclosure.

FIG. 2 is a right-front perspective view of the sprocket of FIG. 1.

FIG. 3 is a front view of the sprocket of FIG. 1.

FIG. 4 is a rear view of the sprocket of FIG. 1.

FIGS. 4A and 4B are cross-sectional views from the perspective of lines A-A and B-B, respectively, of FIG. 4.

FIG. 5 is a side view of the sprocket of FIG. 1.

FIG. 6 is an enlarged view of the area within the broken line circle of FIG. 5.

FIG. 7 is an enlarged view of the area within the broken line circle of FIG. 1.

FIG. 8 is an enlarged view of the area within the broken line circle of FIG. 2.

FIG. 9 is an enlarged view of the area within the broken line circle of FIG. 3.

FIGS. 9A and 9B are cross-sectional views from the perspective of lines A-A and B-B, respectively, of FIG. 9.

FIG. 10 is a left-front perspective view of one example of a sprocket in accordance with the present disclosure engaged with a section of a roller chain.

FIG. 11 is an enlarged view of the area within the broken line circle of FIG. 10.

FIG. 12 is an enlarged view similar to FIG. 11 with an outer link plate removed from the roller chain on an outboard side of the sprocket.

FIG. 13 is a front view of the sprocket of FIG. 10 engaged with a section of a roller chain.

FIG. 14 is an enlarged view of the area within the broken line circle of FIG. 13.

FIG. 14A is a cross-sectional view from the perspective of line A-A of FIG. 14.

FIG. 15 is an enlarged view similar to FIG. 14 with an outer link plate removed from the roller chain on an outboard side of the sprocket.

FIG. 15A is a cross-sectional view from the perspective of line A-A of FIG. 15.

DETAILED DESCRIPTION

In the following detailed description, reference is made to the accompanying drawings which form a part hereof, and in which is shown by way of illustration specific examples in which the disclosure may be practiced. It is to be understood that other examples may be utilized and structural or logical changes may be made without departing from the scope of the present disclosure. The following detailed description, therefore, is not to be taken in a limiting sense, and the scope of the present disclosure is defined by the appended claims.

FIGS. 1 and 2 are left-front and right-front perspective views, respectively, of one example of a sprocket 10 for use as a chainring on a bicycle (not shown). In addition, FIGS. 3 and 4 are front and rear views, respectively, of sprocket 10. Furthermore, FIG. 5 is a side view of sprocket 10, where the side view of FIG. 5 represents left, right, top, and bottom views of sprocket 10, and FIG. 6 is an enlarged view of the area within the broken line circle of FIG. 5.

As illustrated in FIGS. 1-6, sprocket 10 includes a body 12 and a plurality of teeth 14 radially, outwardly extending, projecting from body 12. In one example, body 12 includes one or more mounting holes 16 for mounting or securing sprocket 10 to a crank assembly (not shown) of a bicycle. It is understood that the number, size, form, configuration, and/or arrangement of mounting holes 16 may vary. In addition, sprocket 10 may include one or more other features (in addition to and/or in place of mounting holes 16) to mount or secure sprocket 10 to a crank assembly.

In one example, sprocket 10 has a rotational axis R and a centerline C normal to rotational axis R such that sprocket 10 rotates about rotational axis R in a plane coinciding with centerline C normal to rotational axis R. In the example illustrated, sprocket 10 rotates in a drive direction D about rotational axis R such that teeth 14 each have a drive side 18 and a non-drive side 20 relative to drive direction D. In addition, teeth 14 each have opposite lateral sides 22 relative to centerline C and drive direction D. Although illustrated as being circular in shape, sprocket 10 may be non-circular, for example, elliptical, pseudo-elliptical, oval, ovoid, parabolic, etc.

The front view of FIG. 3 represents an outboard side 24 of sprocket 10 and the rear view of FIG. 4 represents an inboard side 26 of sprocket 10 when sprocket 10 is mounted or secured to a crank assembly of a bicycle and rotated (driven) in drive direction D. In one example, teeth 14 of sprocket 10 are substantially symmetrical about centerline C such that a shape or profile of teeth 14 on outboard side 24 and inboard side 26 substantially mirror each other. In one example, as described below, teeth 14 of sprocket 10 engage a roller chain such that rotation of sprocket 10 in drive direction D imparts movement to the roller chain.

In the example illustrated in FIGS. 1-6, teeth 14 include alternating teeth of different width or thickness. More specifically, in one example, and with reference to FIGS. 4A and 4B, teeth 14 include a plurality of first teeth 100 each having a first width W1 (defined as or formed by a maximum width between opposite lateral sides 22) and a plurality of second teeth 200 each having a second width W2 (defined as or formed by a maximum width between opposite lateral sides 22) such that second width W2 is greater than first width W1.

In one example, first teeth 100 and second teeth 200 are alternately arranged with one second tooth 200 positioned between two first teeth 100 (or one first tooth 100 positioned between two second teeth 200). As such, first teeth 100 and second teeth 200 form a sequence or series of alternating wide and narrow teeth about a periphery of sprocket 10. In one example, first teeth 100 and second teeth 200 each include an even number of teeth and, more specifically, each include the same number of teeth.

In one example, as illustrated in FIGS. 5 and 6, first teeth 100 and second teeth 200 are aligned along centerline C. In addition, in one example, first teeth 100 and second teeth 200 are substantially symmetrical about centerline C. As such, the shapes and/or profiles of first teeth 100 and second teeth 200 are substantially symmetrical about centerline C.

FIGS. 7, 8, and 9 are enlarged views of the areas within the broken line circles of FIGS. 1, 2, and 3, respectively. More specifically, FIGS. 7, 8, and 9 illustrate the shapes and/or profiles of first teeth 100 and second teeth 200 from the perspective of outboard side 24 of sprocket 10. As teeth 14 of sprocket 10 are substantially symmetrical about centerline C, the illustrations and associated descriptions of the shapes and/or profiles of first teeth 100 and second teeth 200 from the perspective of outboard side 24 of sprocket 10 are also applicable to the shapes and/or profiles of first teeth 100 and second teeth 200 from the perspective of inboard side 26 of sprocket 10.

In one example, as illustrated in FIGS. 7, 8, and 9, first teeth 100 each terminate with a tip portion 102, and include a base or root portion 104 extended from body 12 of sprocket 10 and an intermediate portion 106 formed or defined between root portion 104 and tip portion 102. Intermediate portion 106 provides a lateral surface 108 of first teeth 100 such that first width W1 (FIG. 9A) is formed by or defined as a maximum width between lateral surface 108 as provided on opposite sides 22 of first teeth 100. In addition, first teeth 100 each include a front (leading) or drive-side surface 110 and a rear (trailing) or non-drive-side surface 120.

In one example, drive-side surface 110 of first teeth 100 includes and/or is formed or defined by a drive-side face 112 and a drive-side flank 114, and non-drive-side surface 120 of first teeth 100 includes and/or is formed or defined by a non-drive-side face 122 and a non-drive-side flank 124. In one example, drive-side face 112 extends between a top land 130 of tip portion 102 and drive-side flank 114, and drive-side flank 114 extends between drive-side face 112 and a bottom land 150 formed and/or defined between adjacent teeth. In addition, non-drive-side face 122 extends between top land 130 of tip portion 102 and non-drive-side flank 124, and non-drive-side flank 124 extends between non-drive-side face 122 and bottom land 150 formed and/or defined between adjacent teeth.

In one example, tooth tip radii 132 and 134 provide a transition between top land 130 and drive-side face 112 of drive-side surface 110 and non-drive-side face 122 of non-drive-side surface 120, respectively. In addition, in one example, a width W11 (FIG. 6) of top land 130 is substantially uniform and coincides with and/or is substantially the same as a width of tooth tip radii 132 and 134 at the transition between top land 130 and drive-side face 112 of drive-side surface 110 and non-drive-side face 122 of non-drive-side surface 120.

In one example, first teeth 100 each include a lateral tooth tip chamfer 136 formed and/or defined between intermediate portion 106 and tip portion 102. As such, lateral tooth tip chamfer 136 reduces a width of and provides a taper to first teeth 100 in a radial direction from lateral surface 108 of intermediate portion 106 to top land 130 of tip portion 102. Thus, width W11 (FIG. 6) of top land 130 of first teeth 100 is less than width W1 (FIG. 6) of intermediate portion 106 of first teeth 100 as defined by lateral surface 108.

In one example, as illustrated in FIGS. 7, 8, and 9, second teeth 200 each terminate with a tip portion 202, and include a base or root portion 204 extended from body 12 of sprocket 10 and a intermediate portion 206 formed or defined between root portion 204 and tip portion 202. Intermediate portion 206 provides a lateral surface 208 of second teeth 200 such that second width W2 (FIG. 9B) is formed by or defined as a maximum width between lateral surface 208 as provided on opposite sides 22 of second teeth 200. In addition, second teeth 200 each include a front (leading) or drive-side surface 210 and a rear (trailing) or non-drive-side surface 220.

In one example, drive-side surface 210 of second teeth 200 includes and/or is formed or defined by a drive-side face 212 and a drive-side flank 214, and non-drive-side surface 220 of second teeth 200 includes and/or is formed or defined by a non-drive-side face 222 and a non-drive-side flank 224. In one example, drive-side face 212 extends between a top land 230 of tip portion 202 and drive-side flank 214, and drive-side flank 214 extends between drive-side face 212 and bottom land 150 formed and/or defined between adjacent teeth. In addition, non-drive-side face 222 extends between top land 230 of tip portion 202 and non-drive-side flank 224, and non-drive-side flank 224 extends between non-drive-side face 222 and bottom land 150 formed and/or defined between adjacent teeth.

In one example, tooth tip radii 232 and 234 provide a transition between top land 230 and drive-side face 212 of drive-side surface 210 and non-drive-side face 222 of non-drive-side surface 220, respectively. In addition, in one example, a width W21 (FIG. 6) of top land 230 is substantially uniform and coincides with and/or is substantially the same as a width of tooth tip radii 232 and 234 at the transition between top land 230 and drive-side face 212 of drive-side surface 210 and non-drive-side face 222 of non-drive-side surface 220.

In one example, second teeth 200 each include a lateral tooth tip chamfer 236 formed and/or defined between intermediate portion 206 and tip portion 202. As such, lateral tooth tip chamfer 236 reduces a width of and provides a taper to second teeth 200 in a radial direction from lateral surface 208 of intermediate portion 206 to top land 230 of tip portion 202. Thus, width W21 (FIG. 6) of top land 230 of second teeth 200 is less than width W2 (FIG. 6) of intermediate portion 206 of second teeth 200 as defined by lateral surface 208.

In one example, as illustrated in FIG. 6, width W21 of top land 230 of second teeth 200 is greater than width W11 (FIG. 6) of top land 130 of first teeth 100. Width W21 of top land 230, however, may be less than width W11 of top land 130. In addition, width W21 of top land 230 and width W11 of top land 130 may be substantially the same (substantially equal).

In one example, second teeth 200 each include a lateral tooth root chamfer 238 formed and/or defined between intermediate portion 206 and root portion 204. As such, lateral tooth root chamfer 238 reduces a width of and provides a taper to second teeth 200 along a radial direction from lateral surface 208 to root portion 204. Thus, a width of root portion 204 of second teeth 200 is less than width W2 (FIG. 4B) of intermediate portion 206 of second teeth 200 as defined by lateral surface 208.

In one example, second teeth 200 each include a drive-side relief 240 and a non-drive-side relief 250. In one example, drive-side relief 240 extends and provides a transition between drive-side surface 210 and lateral surface 208, and extends and provides a transition between drive-side surface 210 and lateral tooth tip chamfer 236 and lateral tooth root chamfer 238. In addition, non-drive-side relief 250 extends and provides a transition between non-drive-side surface 220 and lateral surface 208, and extends and provides a transition between non-drive-side surface 220 and lateral tooth tip chamfer 236 and lateral tooth root chamfer 238. As such, drive-side relief 240 extends and provides transition between and among drive-side surface 210, lateral surface 208, lateral tooth tip chamfer 236, and lateral tooth root chamfer 238, and non-drive-side relief 250 extends and provides transition between and among non-drive-side surface 220, lateral surface 208, lateral tooth tip chamfer 236, and lateral tooth root chamfer 238.

In one example, drive-side relief 240 includes a drive-side face relief 242 and a drive-side flank relief 244, and non-drive-side relief 250 includes a non-drive-side face relief 252 and a non-drive-side flank relief 254. As such, in one example, drive-side face relief 242 extends and provides a transition between drive-side face 212, lateral tooth tip chamfer 236, and lateral surface 208, and drive-side flank relief 244 extends and provides a transition between drive-side flank 214, lateral surface 208, and lateral tooth root chamfer 238. More specifically, drive-side face relief 242 extends from drive-side face 212 to lateral tooth tip chamfer 236 and lateral surface 208, and drive-side flank relief 244 extends from drive-side flank 214 to lateral surface 208 and lateral tooth root chamfer 238. In addition, non-drive-side face relief 252 extends and provides a transition between non-drive-side face 222, lateral tooth tip chamfer 236, and lateral surface 208, and non-drive-side flank relief 254 extends and provides a transition between non-drive-side flank 224, lateral surface 208, and lateral tooth root chamfer 238. More specifically, non-drive-side face relief 252 extends from non-drive-side face 222 to lateral tooth tip chamfer 236 and lateral surface 208, and non-drive-side flank relief 254 extends from non-drive-side flank 224 to lateral surface 208 and lateral tooth root chamfer 238.

In one example, second teeth 200 are asymmetrical about a plane P (FIG. 9, 9B) extended radially from rotational axis R (FIG. 5) through a tooth root center and tooth tip center of a respective tooth. More specifically, in one example, asymmetry of second teeth 200 includes lateral surface 208 being offset in a direction opposite drive direction D relative to plane P. More specifically, in one example, a midline M of lateral surface 208 is offset (“shifted”) in a direction opposite drive direction D relative to plane P. In addition, in one example, asymmetry of second teeth 200 includes a maximum width W3 (FIG. 9B) of drive surface 210 being greater than a maximum width W4 (FIG. 9B) of non-drive-side surface 220.

In one example, second teeth 200 are symmetrical about a tooth centerline CT (FIG. 9B) extended through drive-side surface 210 and non-drive-side surface 220. More specifically, in one example, tooth centerline CT intersects (bisects) drive-side surface 210 and non-drive-side surface 220, and is oriented substantially perpendicular to plane P. Thus, in one example, second teeth 200 are asymmetrical about plane P (FIG. 9, 9B) and symmetrical about tooth centerline CT (FIG. 9B). In one example, tooth centerline CT coincides with centerline C of sprocket 10 (FIG. 5, 6).

In one example, drive-side relief 240 (including drive-side face relief 242 and drive-side flank relief 240) includes and/or is formed or defined by a surface 246 extended between drive-side surface 210 (including drive-side face 212 and drive-side flank 214) and lateral surface 208, and non-drive-side relief 250 (including non-drive-side face relief 252 and non-drive-side flank relief 254) includes and/or is formed or defined by a surface 256 extended between non-drive-side surface 220 (including non-drive-side face 222 and non-drive-side flank 224) and lateral surface 208.

More specifically, in one example, in cross-sectional view, surface 246 is an arcuate (non-linear) surface such that drive-side relief 240 provides a concave relief or fillet between drive-side surface 210 and lateral surface 208 (and lateral tooth tip chamfer 236 and lateral tooth root chamfer 238), and surface 256 is an arcuate (non-linear) surface such that non-drive-side relief 250 provides a concave relief or fillet between non-drive-side surface 220 and lateral surface 208 (and lateral tooth tip chamfer 236 and lateral tooth root chamfer 238).

In one example, surface 246 is formed by an arc having a radius R1 intersecting lateral surface 208 and drive-side surface 210, and surface 256 is formed by an arc having a radius R2 intersecting lateral surface 208 and non-drive-side surface 220. As such, in one example, asymmetry of second teeth 200 includes a distance to a point of intersection of radius R1 at drive-side surface 210 relative to lateral surface 208 being less than a distance to a point of intersection of radius R2 at non-drive-side surface 210 relative to lateral surface 208. Thus, a degree or amount of asymmetry of second teeth 200 may be varied based on where radius R1 and radius R2 intersect the adjoining surfaces (i.e., lateral surface 208 and drive-side surface 210, and lateral surface 208 and non-drive-side surface 220). In one example, radius R1 and radius R2 are substantially the same (substantially equal). Radius R1, however, may be greater than or less than radius R2. As such, radius R1 and radius R2 and/or points of intersection of radius R1 and radius R2 may be selected to achieve various results of clearance (e.g., link plate clearance) and width of contact (e.g., drive-side contact and/or lateral surface contact).

FIGS. 10-15 illustrate one example of sprocket 10 engaged with a section of a roller chain 50. Sprocket 10 engages roller chain 50 such that rotation of sprocket 10 about rotational axis R (FIG. 5) in drive direction D imparts movement to roller chain 50. In one example, roller chain 50 includes and/or is formed by alternating, overlapping pairs of laterally spaced apart outer link plates 52 and laterally spaced apart inner link plates 54.

In one example, cylindrical rollers 56 are provided between inner link plates 54 at opposite ends of inner link plates 54, and outer link plates 52 and inner link plates 54 are pivotally interconnected by link pins 58 extended through rollers 56 and overlapping, opposite ends of outer link plates 52 and inner link plates 54. As such, inner link plates 54 are interleaved with outer link plates 52, and outer link plates 52 and inner link plates 54 form alternating teeth receiving openings or spacings of different width. More specifically, in one example, outer link plates 52 and inner link plates 54 form alternating wide and narrow teeth receiving openings 60 and 62, respectively.

In one example, alternating wide and narrow teeth receiving openings 60 and 62 of roller chain 50 are engaged by respective alternating wide and narrow teeth 14 of sprocket 10. More specifically, second (wide) teeth 200 of sprocket 10 engage wide teeth receiving openings 60, and first (narrow) teeth 100 of sprocket 10 engage narrow teeth receiving openings 62. As such, in one example, width W2 (FIG. 4B) of second teeth 200 and width W1 (FIG. 4A) of first teeth 100 correspondingly cooperate with wide teeth receiving openings 60 and narrow teeth receiving openings 62, respectively, of roller chain 50.

In one example, a relief 152 is provided in bottom land 150 between adjacent teeth 100 and 200. In one example, relief 152 extends between drive-side 18 of one tooth and non-drive-side 20 of an adjacent tooth (or between non-drive-side 20 of one tooth and drive-side 18 of an adjacent tooth). In one example, separate reliefs 152 are provided in bottom land 150 on outboard side 24 and inboard side 26 of sprocket 10.

In one example, relief 152 includes and/or is formed or defined by an arcuate chamfer formed between bottom land 150 and body 12 of sprocket 10, and between the drive-side flank of one tooth and the non-drive-side flank of an adjacent tooth. More specifically, in one example, one relief 152 extends from drive-side flank 114 of first teeth 100 to non-drive-side flank 224 and non-drive-side flank relief 254 of an adjacent second tooth 200, and another relief 152 extends from drive-side-flank 214 and drive-side flank relief 244 of second teeth 200 to non-drive-side flank 124 of an adjacent first tooth 100. Providing relief 152 in bottom land 150 between adjacent teeth 100 and 200 helps to clear debris (e.g., mud) from bottom land 150 so as to clear an area for rollers 56 of roller chain 50.

In one example, as illustrated in FIGS. 14 and 14A and FIGS. 15 and 15A, when sprocket 10 is engaged with roller chain 50 and rotated (driven) in drive direction D, contact between teeth 14 of sprocket 10 and roller chain 50 includes contact between drive side 18 of teeth 14 and roller chain 50 and between lateral sides 22 of teeth 14 and roller chain 50. More specifically, when sprocket 10 is engaged with roller chain 50 and rotated (driven) in drive direction D, contact between second teeth 200 of sprocket 10 and roller chain 50 includes contact (direct contact) between drive-side surface 210 and rollers 56, and contact (incidental contact) between lateral surface 208 and outer link plates 52.

In addition, in one example, when sprocket 10 is engaged with roller chain 50 and rotated (driven) in drive direction D, tension is generated on roller chain 50 in a direction of drive direction D such that, in one example, any stretch or “play” in roller chain 50 results in reduced (minimal) contact between non-drive-side surface 220 and rollers 56 of roller chain 50 (as compared to contact between drive-side surface 210 and rollers 56). As such, in one example, width W4 of non-drive-side surface 220 is reduced (relative to width W3 of drive-side surface 210), and lateral surface 208 is extended toward non-drive-side surface 220 to increase (maximize) a surface area of lateral surface 208, as manifested in the asymmetry of second teeth 200.

By including drive-side relief 240 at drive side 18 of second teeth 200, as illustrated and described herein, contact between drive-side surface 210 of second teeth 200 and rollers 56 of roller chain 50 may be maintained (maximized) while maintaining clearance between second teeth 200 and inner link plates 54 of roller chain 50. In addition, with the asymmetry of second teeth 200, as illustrated and described herein, contact between lateral surface 208 of second teeth 200 and outer link plates 52 of roller chain 50 may be maintained (maximized) while maintaining clearance between second teeth 200 and inner link plates 54 of roller chain 50. More specifically, with a relief area formed by drive-side relief 240 being greater than a relief area formed by non-drive side relief 250, drive-side surface 210 may fit more deeply within an area (“pocket”) formed between inner link plates 54 and rollers 56, so as to maximize (increase) contact between drive-side surface 210 and rollers 56 of roller chain 50.

Thus, by maintaining (maximizing) contact between drive-side surface 210 of second teeth 200 and rollers 56 of roller chain 50, and/or by maintaining (maximizing) contact between lateral surface 208 of second teeth 200 and outer link plates 52 of roller chain 50, retention of roller chain 50 on sprocket 10 may be maintained (improved). In addition, by maintaining (maximizing) contact between drive-side surface 210 of second teeth 200 and rollers 56 of roller chain 50, and/or by maintaining (maximizing) contact between lateral surface 208 of second teeth 200 and outer link plates 52 of roller chain 50, wear of sprocket 10 may be minimized (improved).

Although specific examples have been illustrated and described herein, it will be appreciated by those of ordinary skill in the art that a variety of alternate and/or equivalent implementations may be substituted for the specific examples shown and described without departing from the scope of the present disclosure. This application is intended to cover any adaptations or variations of the specific examples discussed herein. Therefore, it is intended that this disclosure be limited only by the claims and the equivalents thereof. 

What is claimed is:
 1. A sprocket, comprising: teeth radially projecting from a body, the teeth including first teeth having a first maximum width and second teeth having a second maximum width greater than the first maximum width alternately arranged with the first teeth, the sprocket to rotate in a drive direction about a rotational axis, and the second teeth being asymmetrical about a plane extended radially from the rotational axis, the second teeth having a drive-side surface relative to the drive direction, a lateral surface at the second maximum width, and a drive-side relief between the drive-side surface and the lateral surface, the drive-side relief comprising a non-linear surface.
 2. The sprocket of claim 1, wherein the first and second teeth comprise a series of alternating wide and narrow teeth relative to each other.
 3. The sprocket of claim 1, further comprising: the second teeth being substantially symmetrical about a centerline oriented substantially perpendicular to the plane extended radially from the rotational axis.
 4. The sprocket of claim 1, wherein the drive-side relief comprises a concave fillet between the drive-side surface and the lateral surface.
 5. The sprocket of claim 1, further comprising: the second teeth having a non-drive-side surface relative to the drive direction, and a non-drive-side relief between the non-drive-side surface and the lateral surface, the non-drive-side relief comprising a non-linear surface.
 6. The sprocket of claim 5, wherein the non-drive-side relief comprises a concave fillet between the non-drive-side surface and the lateral surface.
 7. The sprocket of claim 5, wherein a distance to a point of intersection of the drive-side relief at the drive-side surface relative to the lateral surface is less than a distance to a point of intersection of the non-drive-side relief at the non-drive-side surface relative to the lateral surface.
 8. The sprocket of claim 1, further comprising: the second teeth having a lateral tooth tip chamfer between the lateral surface and a tip portion thereof, and a lateral tooth root chamfer between the lateral surface and a root portion thereof, wherein the drive-side relief extends between the drive-side surface, the lateral surface, the lateral tooth tip chamfer, and the lateral tooth root chamfer.
 9. The sprocket of claim 1, wherein the sprocket comprises a chainring.
 10. A sprocket, comprising: first teeth having a first maximum width; and second teeth having a second maximum width greater than the first maximum width, the second teeth alternately arranged with the first teeth, the second teeth having a leading surface relative to a drive direction of the sprocket, a lateral surface at the second maximum width, and a concave relief between the leading surface and the lateral surface, a midline of the lateral surface being offset relative to a plane extended radially through a center of a respective tooth.
 11. The sprocket of claim 10, wherein the midline of the lateral surface is offset in a direction opposite the drive direction of the sprocket.
 12. The sprocket of claim 10, wherein the concave relief comprises an arcuate surface between the leading surface and the lateral surface.
 13. The sprocket of claim 10, wherein the second teeth are substantially symmetrical about a centerline extended through the leading surface.
 14. The sprocket of claim 10, further comprising: the second teeth having a trailing surface relative to the drive direction of the sprocket, and a concave relief between the trailing surface and the lateral surface.
 15. The sprocket of claim 14, wherein a maximum width of the leading surface is greater than a maximum width of the trailing surface.
 16. A sprocket, comprising: alternating first and second teeth, the first teeth having a first maximum width, and the second teeth having a second maximum width greater than the first maximum width, the second teeth having a drive side and a non-drive side relative to a drive direction of the sprocket, a drive-side surface at the drive side, a non-drive-side surface at the non-drive side, and a drive-side relief at the drive side, a maximum width of the drive-side surface being greater than a maximum width of the non-drive-side surface, and the drive-side relief comprising a fillet.
 17. The sprocket of claim 16, further comprising: the second teeth being asymmetrical about a plane extended radially from a rotational axis of the sprocket, and the second teeth being substantially symmetrical about a centerline oriented substantially perpendicular to the plane.
 18. The sprocket of claim 16, further comprising: the second teeth having a lateral surface at the second maximum width, the drive-side relief extended between the drive-side surface and the lateral surface.
 19. The sprocket of claim 18, further comprising: the lateral surface having a midline offset in a direction opposite the drive direction of the sprocket.
 20. The sprocket of claim 16, further comprising: the second teeth having a non-drive-side relief at the non-drive side, the non-drive-side relief comprising a fillet. 